From: Satyam Sharma <satyam@infradead.org>

A full register dump along with stack backtrace would make the "scheduling
while atomic" message more helpful.  Use show_regs() instead of
dump_stack() for this.  We already know we're atomic in here (that is why
this function was called) so show_regs()'s atomicity expectations are
guaranteed.

Also, modify the output of the "BUG: scheduling while atomic:" header a bit
to keep task->comm and task->pid together and preempt_count() after them.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/sched.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff -puN kernel/sched.c~sched-use-show_regs-to-improve-__schedule_bug-output kernel/sched.c
--- a/kernel/sched.c~sched-use-show_regs-to-improve-__schedule_bug-output
+++ a/kernel/sched.c
@@ -63,6 +63,7 @@
 #include <linux/unistd.h>
 
 #include <asm/tlb.h>
+#include <asm/irq_regs.h>
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -3401,12 +3402,19 @@ EXPORT_SYMBOL(sub_preempt_count);
  */
 static noinline void __schedule_bug(struct task_struct *prev)
 {
-	printk(KERN_ERR "BUG: scheduling while atomic: %s/0x%08x/%d\n",
-		prev->comm, preempt_count(), prev->pid);
+	struct pt_regs *regs = get_irq_regs();
+
+	printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
+		prev->comm, prev->pid, preempt_count());
+
 	debug_show_held_locks(prev);
 	if (irqs_disabled())
 		print_irqtrace_events(prev);
-	dump_stack();
+
+	if (regs)
+		show_regs(regs);
+	else
+		dump_stack();
 }
 
 /*
_